Martian soil samples will be collected and brought back to Earth as part of the first round-trip mission to the red planet, European and US scientists have announced.
Nasa and the European Space Agency (Esa) today signed an agreement to plan the endeavour, which could reveal if life exists or existed on Mars.
So far, efforts to explore the planet have relied on analysis of Martian soil by robotic rovers and static landers, which send data back to Earth.
But collecting samples and returning them to Earth would enable detailed examinations in laboratories using instruments that are currently too large or power-hungry to be carried the 34 million miles.
The mission is likely to involve samples obtained by a rover being loaded onto an ascent vehicle which would blast off from the Martian surface and then deploy a descent module which would parachute down to Earth.
The samples would then be subject to strict quarantine, described as “planetary protection”, aimed at preventing contamination of Earth in the event they contained Martian organisms.
Dave Parker, director of human and robotic exploration at Esa, said: “It’s very important that every mission we send to Mars discovers something slightly unusual.
“It’s on the basis of that that we tend to plan the next mission or next missions.”
Nasa said the two agencies would be seeking commercial partners to collaborate on any any round-trip mission.
The 2020 rover mission is expected to help prepare a Mars Sample Return mission, by drilling into the surface and caching the cores in containers, although this is designed mainly to act as a demonstration.
Dr Zurbuchen, associate administrator for science, said the sample return mission could also be crucial for later planned human exploration of Mars, which he said Nasa should start thinking about in the 2030s.
"I can imagine a lot of scenarios where the samples are actually critical for how we explore as humans," he said.
In numbers | Mars
Esa's Trace Gas Orbiter (TGO) is currently in Martian orbit preparing its instruments.
It will contribute to the question of alien life by mapping the distribution in the atmosphere of methane gas, which could be produced by Martian organisms, but also by non-biological sources.
Nasa and Esa had previously worked together on a programme to return geological samples from the Red Planet.
In 2009 the agencies agreed to work together on the Mars Joint Exploration Initiative, which may have culminated in the recovery of samples in the 2020s.
In 2011, however, Nasa cancelled its participation in the project amid a budgetary squeeze.
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